Andrew Forrest's Fortescue Metals is seeking to have Gina Rinehart's $390 million takeover attempt on Atlas Iron halted, alleging there are misleading statements and omissions in her company's bid.
A Fortescue company has gone to the Takeovers Panel asking that Redstone - a subsidiary of Ms Rinehart's Hancock Prospecting - be prevented from advancing its takeover of Atlas or acquiring any more shares in the junior miner.
Hancock Prospecting emerged last week as the winner of a three-way battle for Atlas, beating Fortescue and mid-tier player Mineral Resources.
Fortescue subsidiary NCZ has claimed that Redstone's bidder's statement has "misleading statements and material omissions" about its intentions towards Atlas's business, assets and employees.
NCZ also claimed, in details published by the Takeovers Panel on Tuesday, that the Redstone bid omitted details of Hancock Prospecting's intentions towards Atlas's existing debts.
NCZ claimed the combination of alleged misleading statements and omissions, and the structure of the bid, had a "coercive effect" on Atlas shareholders to accept the bid or sell on-market.
The Fortescue company has asked that Redstone be ordered to issue a replacement bidder's statement and cancel acquisitions of Atlas shares made since the original statement was released on June 18.
Hancock responded on Tuesday by saying it will talk to the Takeovers Panel to explain its position.
"We are confident that our proposal is a good offer and we look forward to getting our offer to all Atlas shareholders," Hancock said in a statement.
The Takeovers Panel is yet to decide whether it will consider the NCZ application.
Atlas's assets include rights to potentially valuable undeveloped port capacity in Port Hedland.
Ms Rinehart controls 19.96 per cent of Atlas, while Mr Forrest also has a near-20 per cent stake.